Electroformed inner tube for tank unit



Jan. 24, 1967 w SARGENT 3,299,492

ELECTROFORMED INNER TUBE FOR TANK UNIT Filed Aug. 14, 1963 A H G PROGRAM T BE TANK UNIT ASSEMBLY ASSEMBLY B C D E, F co fim 51 1 12 PLAT 1N6 LEACHING fi iifi O LATHE, MANDREL R0 M TANK ELECTROFORM w T h J a t m 4 'z /m L H H 5 (5 2 5 INVENTOR United States Patent O 3,299,492 ELECTROFORMED INNER TUBE FOR TANK UN IT Raymond W. Sargent, Burlington, Vt., assignor to Sunmonds Precision Products, Inc., Tarrytown, N.Y., a corporation of New York Filed Aug. 14, 1963, Ser. No. 301,961 3 Claims. (Cl. 29-1555) The present invention relates to an electroformed inner tube tank unit which has a profiling accomplished in accordance with the process of the present invention so as to provide thereby varying diameters of uniform or nonuniform length increments which may correspond to the liquid level increment chosen from predetermined profiling data.

More particularly, the invention is directed to a profiled metal tank unit having a capacitance ratio suitable for use in military application, and which is constructed of, as well as having, an electroformed inner tube.

In accordance with a preferred embodiment of the invention the inner tube of the invention is constructed and manufactured by an electroform which is a comparatively inexpensive part of the invention to produce, since the cost of material and electrical current for deposition of material is minimal. Incident to the electroform, there is, however, the problem of providing a suitable matrix on which the electroform is accomplished. The matrix is a male member over which pure nickel of approximately at least 0.004 inch of thickness may be electro-deposited, and also which may be readily removed. Inasmuch as there are undercuts involved in the final configuration, it is obvious that the matrix must be expendable.

Perhaps the outstanding advantages of the new electroform, which is preferably nickel electroform, are that the nickel electroform inherently provides a larger airgap, that no machining is required, that it is satisfactory for high temperature usage (700 F.), that it is light in weight which is substantially one-third of the present fiberglass construction, and that it is unalfected'by moisture and humidity. Also incident to the process of the new invention is the elimination of costly cementing and varnishing operations.

In the new process of forming the inner tube, it is found that the matrix must be either fusible or soluble. Fusible materials for purposes of usage in tank units may include wax or low temperature metals such as those called Cerro metals, while soluble materials may include certain plastics such as polystyrene or acrylics that are readily dissolved, or soluble materials such as aluminum which is readily etched away by means of contact with a caustic compound or solution. In accordance with the present invention, there is provided means for rendering all non-conductive materials conductive on the surface to which the nickel electroform is to be deposited.

An object of the present invention, therefore, is to provide a method of fabrication means and method for providing an inner tube which is a turned aluminum inner tube where small quantities of such are required in production.

A further object of the invention is to produce inner tubes in normal quantities by the machining on an automatic lathe of a matrix of some expendable material such as polystyrene or acrylics that are readily dissolvable. In this connection, it is noted that a lathe may produce this part automatically by it being programmed by a tape or other selective control means.

A further object of the invention is to provide where large numbers of inner tubes are required a method of producing the matrix by a metal mold. This is found to be substantially economical for large quantities.

Other objects and advantages will become apparent 3,299,492 Patented Jan. 24, 1967 from a reading of the following specification and drawings, in which:

FIG. 1 is a schematic diagram illustrating the steps embodied by a method according to the invention;

FIG. 2 is a perspective view illustrating the inner electroformed nickel electrode member on a series of drilled aluminum tube members; and

FIG. 3 is a view partially in elevation and cross-section illustrating the assembled capacitance measuring system.

Referring now to FIG. 1, one preferred embodiment of the invention is making a matrix of aluminum metal in tubular form. Thus, in accordance with the first three steps A, B, C, the aluminum metal in tubular form is then machined down according to the profile law for each particular tank unit, which is done to provide necessary characteristics as used and known for certain military pur poses. Over this aluminum matrix, after being machined in accordance with the profile law and in accordance with step D as shown, a pure nickel thickness of approximately 0.004 inch is electro-deposited over the matrix. With this step completed, we now come to step E to remove the aluminum matrix innermost tube from the outer nickel electro-deposit. This is done by running caustic solutions through the tubular aluminum matrix. Caustic solutions used for this purpose are sodium hydroxide, calcium hydroxide and other similar agents which will attack and disolve away the aluminum, as is well known. Upon complete removal of the aluminum, there is left the electro-deposited nickel which forms an inner electrode 2 as shown in FIG. 2. This overall electrode is of light material and consists of a thin shell of sufiiciently strong material to form the inner tube of an electrode unit 4. This inner tube has been profiled according to the tank unit and is therefore ready for assembly with an outer electrode 6 as designated by the steps F, G, H, in FIG. 1. The inner electrode 2 may be secured to the outer electrode 6 by means of insulated spacers 8 as best shown in FIG. 3. Leads 10, 12 may be brought in to both electrodes at one end of the tank unit. This unit upon completion is immeasurably lighter than comparable Fiberglass units and gives high accuracy. Tests so far have shown that the tank unit as now assembled is capable of withstanding high temperatures and also has undergone severe vibration tests. There appears to be no problem as to strength and durability.

There are other methods of producing embodiment of the present invention. One is to use fusible materials such as waxes or low temperature metal called Cerro metals. These materials are again machined or worked according to a profile law to a designed shape and are used as the matrix over which the nickel is electro-de posited. These ingredients can be removed by tempera tures which would not affect the nickel. One significant advantage of this embodiment is that by accurate machining, close tolerances are obtained and, therefore, there is no necessity for initial adjustment of the unit.

Units themselves will be more accurate than present Fiberglass methods and will eliminate any moisture problems or any green slime problems which are now found present. Units embodying this principle have been made and have been tested showing accurate results. One present limitation to the invention is that for each particular tank unit, there has to be an individual matrix. Methods are available for mass production techniques of the invention. This allows for preparing one matrix for all tank units using similar profile laws in producing a desired shape of matrix.

Thus it is apparent that distinct methods of fabrication present themselves, and these are dependent upon the production requirements of the electroformed inner tube units. For very small quantities, a turned aluminum inner tube is considered, while for normal quantities of units it is plausible to consider machining the matrix on an automatic lathe of some expendable material, as has been described above. In this method, according to steps A, B in FIG. 1, the lathe produces the part automatically as it may be programmed by tape or the selective control means as a full length tube or as a series of drilled slugs of appropriate diameter corresponding to the electroformed sections 2a, 2b, 2c, id as shown in FIG. 2. The series of drilled slugs would be threaded like beads upon a steel rod 14 or the like as shown in FIG. 2. This arrangement also facilitates destruction of the mandrel by allowing the caustic solutions to circulate through the center hole after withdrawal of the steel supporting rod. A further method would include requirements of large metal molds which are found to be economical in producing the matrix.

Thus it is apparent that the preferred embodiment of the invention includes the provision of constructing or forming a matrix upon which there is electroformed an inner tube in accordance with the method of the invention.

It should be understood that the specific method herein described as intended to be representative only, as many changes may be made therein without departing from the clear teachings of the invention. Accordingly, reference should be made to the following claims in determining the full scope of the invention.

What is claimed is:

1. Method of making a matrix inner tube in a tank unit for a lightweight capacitance measuring system comprising:

machining a plurality of tubes of aluminum metal supported in end-to-end relation on a rod member to form the matrix;

electrodepositing substantially pure nickel completely upon and about the aluminum matrix to a thickness of substantially 0.004 inch; removing completely the aluminum metal forming the matrix so that there remains only the outer nickel electrodeposit forming an inner electrode tube, said step of removing including passing caustic solutions through the aluminum matrix tube after removing the rod member therefrom and converting the aluminum to a compound soluble in a liquid state;

assembling the inner electrode tube concentric with and spaced from an outer electrode tube; and

attaching electrodes to the inner electrode tube and the outer electrode tube at a common end thereof.

2. Method of making a matrix inner tube in a tank profile unit for a lightweight capacitance measuring system comprising:

machining a plurality of tubes of aluminum metal supported in end-to-end relationship on an internal removable support member to form the matrix;

electro-depositing a thin layer of nickel completely upon the outside surface of said metal matrix;

removing the removable support member from the matrix;

removing the metal forming the matrix from the outer nickel electro-deposit by passing caustic solutions through the metal matrix tube to form a hollow metal electrode inner tube;

assembling the electrode inner tube concentric with and spaced from an outer electrode tube; and

attaching electrodes to the inner electrode tube and the outer electrode tube at a common end thereof. 3. Method of making a matrix inner tube in a tank profile unit for a lightweight capacitance measuring system comprising:

assembling a plurality of tubes of fusible materials from the group consisting of waxes and low temperature metals including Cerro metals in end-to-end relationship on a supporting member;

electro-depositing a thin layer of nickel completely upon the outside surface of said assembly;

removing the supporting member from the matrix;

removing the fusible material from the electro-deposited nickel by heating the fusible materials so that they are caused to run off to form a hollow electrode inner tube;

assembling the electrode inner tube concentric with and spaced from an outer electrode tube; and

attaching electrodes to the inner electrode tube and the outer electrode tube at a common end thereof.

References Cited by the Examiner UNITED STATES PATENTS CHARLIE T. MOON, Primary Examiner.

WHITMORE A. WILTZ, Examiner.

W. I. BROOKS, Assistant Examiner. 

2. METHOD OF MAKING A MATRIX INNER TUBE IN A TANK PROFILE UNIT FOR A LIGHTWEIGHT CAPACITANCE MEASURING SYSTEM COMPRISING: MACHINING A PLURALITY OF TUBES OF ALUMINUM METAL SUPPORTED IN END-TO-END RELATIONSHIP ON AN INTERNAL REMOVABLE SUPPORT MEMBER TO FORM THE MATRIX; ELECTRO-DEPOSITING A THIN LAYER OF NICKEL COMPLETELY UPON THE OUTSIDE SURFACE OF SAID METAL MATRIX; REMOVING THE REMOVABLE SUPPORT MEMBER FROM THE MATRIX; REMOVING THE METAL FORMING THE MATRIX FROM THE OUTER NICKEL ELECTRO-DEPOSIT BY PASSING CAUSTIC SOLUTIONS THROUGH THE METAL MATRIX TUBE TO FORM A HOLLOW METAL ELECTRODE INNER TUBE; ASSEMBLING THE ELECTRODE INNER TUBE CONCENTRIC WITH AND SPACED FROM AN OUTER ELECTRODE TUBE; AND ATTACHING ELECTRODES TO THE INNER ELECTRODE TUBE AND THE OUTER ELECTRODE TUBE AT A COMMON END THEREOF. 